Limits and persistence cheatsheet
Purpose: Quick reference for variable capabilities and constraints.
Who this page is for
| Audience | Why it matters to you |
|---|---|
| Everyone | Bookmark this page |
| Implementation engineers | Know what you can and cannot do |
Variable capabilities matrix
| Property | prop | eVar | event |
|---|---|---|---|
| Slots | 75 | 250 | 100–1000 |
| Persists beyond the hit | No | Yes (configurable) | N/A |
| Max value length | 100 bytes | 255 bytes | N/A |
| Supports pathing | Yes (if enabled) | No | No |
| Gets conversion credit | No | Yes | N/A |
| Can be classified | Yes | Yes | No |
| Multi-value support | List prop | List var (separate) | No |
| Available in CJA | Merged into fields | Merged into fields | Merged into fields |
Unique value limits
Any variable exceeding ~500,000 unique values in a month starts bucketing overflow into a (Low Traffic) row. This is a real constraint for:
- Internal search terms on a large site
- Anything containing an ID
- Free-text user input
Never put these in a variable
- Member numbers, account numbers, names, email addresses, phone numbers (PII)
- Full URLs with unhashed query strings containing personal data
- Free-text the user typed into a form body
- Anything with unbounded cardinality that you have not thought about (session IDs, timestamps to the second)
See Privacy & Governance for the full rules.
Reading an SDR row
By now you should be able to read this and know exactly what it means:
| ID | Friendly Name | Type | Expiry | Allocation | Value example | Set when |
|---|---|---|---|---|---|---|
| eVar62 | Internal Search Term | eVar | Visit | Most Recent | insurance cover | On search results render |
Translation: *"Slot 62 holds the search term. When someone searches, we write the term. It stays attached to that visitor for the rest of the session, so anything they do afterwards — download a PDF, submit a form, book an appointment — gets credited back to the search that led there. If they search twice, the most recent term takes the credit."*
That sentence is the skill. Everything else is mechanics.
Example SDR entries for Example Super
| ID | Friendly Name | Type | Expiry | Allocation | Value | Set when | ||
|---|---|---|---|---|---|---|---|---|
| eVar10 | Member Persona | eVar | Visit | Most Recent | Member \ | Employer \ | Adviser | On page load |
| eVar62 | Internal Search Term | eVar | Visit | Most Recent | insurance cover | On search results | ||
| eVar81 | Form Name | eVar | Expire on event82 | Original | Make a Complaint | On form start | ||
| prop5 | Page Section | prop | n/a | n/a | member \ | employer | On page load | |
| event20 | Form Submit | Counter | n/a | n/a | CMP-88213 (serialized) | On form submit | ||
| event45 | Search Results Returned | Numeric | n/a | n/a | 24 | On search results |